#include<iostream>
#include<queue>
#include<string>
using namespace std;
typedef pair<int,int>ii;
queue<ii>q[2];
int R,C,K=0,res=0;
bool s;
string d[4000];
const string fr="FR";
int main(){
cin>>R>>C;
q[0]=queue<ii>();
q[1]=queue<ii>();
for(int i=0;i<R;++i){
cin>>ws;
cin>>d[i];
for(int j=0;j<C;++j)if(d[i][j]=='.')++K;
}
s=d[0][0]==fr[1];
d[0][0]='.';
q[s].push({0,0});
while(K<R*C){
//cout<<"---"<<K<<endl;
//cout<<q[0].size()<<' '<<q[1].size()<<endl;
++res;
q[!s]=queue<ii>();
while(!q[s].empty()){
++K;
//cout<<"IT"<<endl;
ii rw=q[s].front();
int x=rw.first,y=rw.second;
//cout<<q[s].size()<<' '<<x<<' '<<y<<endl;
q[s].pop();
if(0<x&&d[x-1][y]!='.'){
q[d[x-1][y]==fr[1]].push({x-1,y});
d[x-1][y]='.';
}
if(x<R-1&&d[x+1][y]!='.'){
q[d[x+1][y]==fr[1]].push({x+1,y});
d[x+1][y]='.';
}
if(0<y&&d[x][y-1]!='.'){
q[d[x][y-1]==fr[1]].push({x,y-1});
d[x][y-1]='.';
}
if(y<C-1&&d[x][y+1]!='.'){
q[d[x][y+1]==fr[1]].push({x,y+1});
d[x][y+1]='.';
}
}
s=!s;
}
cout<<res<<'\n';
return 0;
}
